1. Field of the Invention
The present invention relates to a clutch control system which may be used in a vehicle in which a clutch and a transmission are disposed in a power transmission path from an engine to a vehicle wheel.
2. Description of the Related Art
Japanese Utility Model Application Publication No. 3-69537 discloses an automatic transmission for automobile. On a downward slope, the automatic transmission engages the clutch immediately to prevent increase of vehicle speed due to coast. Also, on an upward slope, the automatic transmission slidingly engages the clutch gradually while keeping an engine output high. The clutch is thereby engaged while preventing lowering of engine speed.
Japanese Patent Application Publication No. 2002-21884 discloses a clutch controller for vehicle. When a vehicle speed becomes not less than a fixed value in a clutch-disengaged state, the clutch controller engages the clutch to apply engine braking to the vehicle in the free running state (coasting state) to perform deceleration. The vehicle speed is determined from an output signal from an output shaft rotation sensor. The output shaft rotation sensor detects the rotation of an output shaft of a transmission.
U.S. Pat. No. 6,171,212 discloses a clutch control for vehicle. With the control, a target clutch torque is calculated based on an engine speed, a transmission input rotational speed, and a throttle valve position. A clutch actuator is controlled based on the target clutch torque. More specifically, a tentative target clutch torque is calculated based on the engine speed and the transmission input rotational speed. On the other hand, a target engine speed is calculated based on the transmission input rotational speed and the throttle valve position. If the actual engine speed is below the target engine speed, the tentative target clutch torque is corrected to calculate the target clutch torque so that the clutch is moved and adjusted in an opening or disengaging direction. If the actual engine speed exceeds the target engine speed, the tentative target clutch torque is corrected to calculate the target clutch torque so that the clutch is moved and adjusted in a closing or engaging direction.